Accelerating pump



Dec. 23, 1941. c. E. MARKHAM ACGELERATING PUMP Filed Sept. 24, 1940 INVENTOR CHARLES E. MARKHAM W U. ATTORNEY ly essential in accurately Patented Dec. 23,1941

, UNITED STATES PATENT OFFICE ACCELERATING PUMP Charles E. Markham, .St. Louis, Mo., assignor to Carter Carburetor Corporation, St. a corporation of Delaware Louis, Mo.,

Application September 24, 1940, .Serial No. 358,049-

4 Claims. (Cl 261-- 34) This invention relates to carburetors for internal combustion engines and more particularly to accelerating devices used in connection therewith.

These devices usually comprise a plunger-type pump which may be actuated by direct interconf nection towthe manually operated carburetor throttle valve or by suction in the carburetor 1:

conduit posterior-to the throttle valve in a man-v ner. well known. The suction operated type has a distinct advantage, over the throttle actuated type in that the accelerating discharge is auto matically varied in accordance with the engine load. I

Certaindisadvantages are inherent, however, in the suction operated type. One of these disadvantages being that the pump will discharge when the engine-is stopped due to loss of, man-' ifold. vacuum. Means for locking the plunger in a loaded position, when the throttle is in a closed position has been proposed to overcome this difliculty. Another disadvantage, however, is

the difliculty offi'building. apump of this type which will deliver the ,exact proportions of its,

total discharge as required. In other words, the spring discharge suction loaded type pump lacks the definite discharge control of the throttle in restriction It and passage 16. I idling system is indicated comprising an idling fuel restriction l1, passage l8, I9, 20, air bleed is controlled by a choke valve It. mounted for rotation on a shaft I I. The outlet of the mixture conduit is controlled bya throttle valve i2 which is mounted for rotation with a throttle valve shaftllw A fuel nozzle H is indicated, receiving fuel from float. chamber 3 through a metering A conventional 2|, restriction .22, air bleed 23, passages 2i and 25, anddischargeport 26. -A conventional float 21 ,acting in a well known manner onan inlet needle valve 28 maintains a substantially con stant level of fuel in chamber 3 as inclicated by the dot-dash line :r:c.

To supply fuel for acceleration, acylinder 29 in chamber 3 is provided having a reciprocating piston 30 ,fitted therein. ,It will be understood that piston 30 may be provided with cup-leathers or any suitable sealing device to prevent leak- .age thereby. An inlet passage-3|, 32 from chamberu3 to the lower part of cylinder is provided. Thispassage is controlled by an interconnected type, a feature which is particular- 1 controlling comparatively small discharges.

The present invention hasfor lest the provision of an accelerating device in which the advantages of bothjoi'the above mentioned types are incorporated and in which ,the disadvantages of these separate typesare, ob-.

viated.

Other objects and advantages will appear in,

and accompanying tubes 5 and I supported therein. Attached tothe top of member I is a combination fuel chamber cover and air inlet gasket 8 which has an air inlet 9 formed therethrough. The air inlet an its primary oblet-check valve 33.. Fuel is'discharged from cylinder .29 into the mixing conduit through passages 34. 35, 36 and discharge nozzle 31. A discharge check valve 38 is provided. A check con trolled air bleed 39 to passage 36 is provided to prevent pull-over due to suction .in the mixture conduit.

Piston carriesiirmly attached thereto an upper, smaller concentric piston 40 which reciprccates in a cylinder ll formed in the upper casting 8. 'The upper end of cylinder 4| como municates with the mixing conduit 2 posterior to the throttle valve through passages 42, 43," and 44. By this arrangement thepiston 30 is drawn upward by suction to fill the cylinder 29 with fuel. A spring 45 inthe upper part of cylinder ll which normally urgesv thefpiston assembly downward to its discharge strokeis'provided.

Formed as a part'of piston-M and extending downwardly through'the body casting is a plunger rod which engages'one end of a rocker arm 41 which is pivoted at 48." The opposite end of rocker arm 41 is acted upon by a cam 49 rigidly attached to the throttle valv'e shaft i3, By this arrangement, a definite maximum jdischarge stroke of the accelerating device for a given throttle opening is ,obtained. Rising upwardly from the bottom of cylinder-29 to a point substantially above fuel level'isv a tube member 53 which acts, as a "guide for rod and prevents leakage of fuel. The piston 30 is also provided with a central perforation which slidably receives the guide member 50.

In operation, when the throttle valve is opened to accelerate the engine there will be a drop in vacuum in the induction system posterior to the throttle, the amount depending upon the load on the engine and the rate and extent of throttle opening. Assuming the engine has the usual motor vehicle load, it is obvious that there will be less drop in vacuum for a given rate of throttle opening if the vehicle is descending an incline than if it were ascending. Under acceleration with light engine loads, less accelerating fuel is required and with the arrangement shown less fuel will be delivered.

On the other hand, it will be appreciated that variable friction and spring rate tolerances are encountered in production and that for slight accelerating discharges, which amounts must be accurate, the definite limitation of the discharge stroke for a given throttle opening, which is provided in this arrangement, permits wider manufacturing tolerances and, therefore, more economical production.

The foregoing description and accompanying drawing are intended to be illustrative and not limiting and the use of all modifications within the scope of the appended claims is contemplated.

I claim:

1. In a carburetor having a vertical mixture conduit, 8. throttle valve mounted on a transthe lower part thereof, said piston having a cen-- tral perforation adapted to slidably receive said guide, an operating rod extending from the exterior below said fuel chamber upwardly through saidguide to a point above said guide and having a downwardly extending portion exterior of said guide member and attached at its lower end to said piston, an eccentric mounted on said throttle shaft, a rocking arm between said eccentric and the lower end of said operating rod, and a spring bearing against said cover and the upper end of said operating rod to urge said piston downward.

2. In a device of the class described, a constant level fuel chamber, an accelerating well in said chamber, a vertical guide member centrally located in said well and rising from the bottom thereof to a point substantially above the level of fuel, a piston constructed and arranged to displace fuel from the lower end of said well and having a central perforation adapted to slidably receive said guide, said guide member and the bottom of said well being provided with a continuous longitudinal bore therethrough, and an operating rod slidably fitted in said bore and extending from the exterior below said well to a point substantially above the. upper end of said guide member and having an integral portion thereof extending downward from its upper end exterior of said guide member and rigidly attached to said piston.

3. In a device of the class described, a pair of opposed vertical cylinders, the lower of said cylinders being a pumping cylinder and being arranged to receive and discharge liquid fuel from its head end, the other of said cylinders having a connection from its head end to a source of varying suction, a composite hollow piston having a head at both ends and being arranged to work in said opposing cylinders, a longitudinal guide member centrally located in said lower cylinder being attached to the head thereof and extending beyond the upward travel of the lower end of said piston, the lower head of said piston being centrally perforated to slidably receive said guide, said lower cylinder head and said guide member having a longitudinal bore extending therethrough, a' control rod extending from the exterior below said lower cylinder through the bore in said lower cylinder head and said guide member and being attached to the upper head of said piston, and a pump discharging spring in the head end of said upper cylinder.

4. In a carburetor having a vertical mixture conduit, a constant level fuel chamber adjacent said conduit, a throttle valve in said conduit below said chamber, an accelerating fuel well in said chamber, a vertical. guide member centrally located in said well and rising from the bottom thereof to a point substantially above the level of fuel, said guide member and the bottom of said well being provided with a central continuous bore extending from the upper end of said guide member'to the exterior below said fuel chamber, a cup-shaped piston arranged to displace fuel from the lower part of said Well, said piston having a central perforation therethrough adapted to slidably receive said guide, an operating rod extending from the exterior below said chamber through said guide and above the upper end thereof, said rod having a portion extending downwardly f1 om its upper end surrounding said guide member and being attached to said piston, and an operating connection between said throttle and the lower end of said rod.

CHARLES E. MARKHAM. 

